1. Field of the Invention
The invention relates to a novel liquid crystal compound useful as a material for a liquid crystal display device, and a liquid crystal composition containing the compound. More specifically, it relates to a novel liquid crystal compound that has a low viscosity, favorable compatibility with other liquid crystal compounds, has a suitable refractive index anisotropy and a suitable dielectric anisotropy, and is capable of providing steep electrooptical characteristics with respect to an applied voltage upon using in a liquid crystal display device, and relates to a liquid crystal composition containing the compound, and a liquid crystal display device containing the liquid crystal composition.
2. Related Art
Active matrix (AM) type or passive matrix (PM) type liquid crystal display devices driven in such modes as TN, STN, PC, ECB, OCB, IPS, VA and so forth have been developed, and as a liquid crystal compound used in the liquid crystal display devices, terphenyl derivatives having alkenyl have been synthesized. For example, JP H11-61132 A/1999 discloses a compound represented by formula (s-1) shown below and a composition containing the compound. EP 1126006A discloses compounds represented by formulas (s-2) and (s-3) shown below, JP H11-43450 A/1999 discloses compounds represented by formulas (s-4) and (s-5) shown below, and JP 2001-11456 A/2001 discloses compounds represented by formulas (s-6) shown below.
However, the compounds represented by formulas (s-1), (s-6) have a high viscosity. The compounds represented by formulas (s-2) and (s-3) have a tendency of having low chemical stability. The compounds represented by formulas (s-4) and (s-5) have strong smectic property to cause deposition of crystals at a low temperature in some cases.
